Motor control.



D. L. LINDQUIST. MOTOR CONTROL.

Arrmouxox num nr 7, noa.

A980, 109'.' Patented De@ 27, 1910.

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UNITED sTATEs PATENT OFFICE.

' DAVID Iz. LINDQIST, 0F YONKERS, NEW YORK, ASSIGNOR TO OTIS-IELIEWZA'IOIR COM- PANY. 0F JERSEY CITY, NEW JERSEY, .A CORPORATION 0FNEW JERSEY.

MOTOR CONTROL.

Specification of Letters Patent. Patented D00. 27, 1910.

Application led'May 7, 1908. Serial No. 431,498l i 'To all whom it mayconcern:

and useful Improvement in Motor Control,

of which the following is a specification.

My lnvention relates to means for controlling electric motors of thealternating current type, which are adapted to be operated bysinglephase currents or polyphase currents.

Oneof-the objects of my invention is the provlsion of a simple andeflicient' alternatlng current brake in combination with an alternatingcurrent motor startin device.

present invention to provide a brake for an alternating current motor inconnection with an alternating current motor starting device to permitsaid brake vto be operated 4with minimum consum tion of current.

Other objects o my invention will appear hereinafter, `the. novelcombinations of elements being pointed out in the claims.

My inventlon is shown diagrammatically in Figure 1 as applied to a threephase in- Iduction motor, but my invention is also 'adaptable totwo-phase, motors and alternat-mg current motors of other types. Fig.

2 shows a brake a paratus which is well adapted for use Witii myinvention.

Referring to vF ig. 1, 39, 17 and 41 designatey the mains whicharevconnected through the manual switch 20 b Way of the leads 48, 5 and10, respectilye y, to the terminals motor. The secondary or rotorwinding of the stator 'winding 21 -of the induction 22 has kitsterminals connected by the leads 18, 15 and 16, respectively, to theterminals m,

` "-fn. and 0 of the starting resistance R. .This

4'starting resistance may be star-connected, `.c'lelta-connected, orvaried as desired. Preferably it is divided in to a number of sectionsso that may be cut out gradually in U in Fig. 2 1s similar to that aseries of steps by means of electric switches successively operated inany well known manner. In this instance I have shown only two sectionsin each of the branches ofthe star-connected resistance R, and the wires31, 32 and 33 connected respectively between .the points h, g and 7c,and the fixed contacts a, a and a of the electric switch S. For the sakeof simplicity, I have shownbut a single switch, but as indicated in myPatent No. 733,550, granted July 14, 1903, for

an improvement 1n controlling devices forv alternating current motors,there may be a plurality of suchswitches.

The means for operatin theswitch S comprises an operating e ectromagnetA and a holding electromagnet B. The cores of-these electromagnets aredesignated land 2, respectively, and are connected with each 1 and 2andthe bridge ieee D, which, itis More particularly it is the ob]ect ofthev evident, all move toge't er. The core 1 is so positioned with.respect toits solenoid 8 that when the latter is energized, said corewill be drawn upwardly; but the core 2 normally occu iessuch avpositionwith respect to its sollenoid 9 that thelatter, when energized,-wi"ltend to hold the' core 2 in its lowermost position. If desired, the.electroma ets A-and B may be combined in a sing e electromagnet havintwo windings 'pointsll and 24. The vwindin s 28 and 29 each other,`

arealso connected in series wit and the wires 26 \and.30 between thelead 48 andwire 25, being connected to the same at the points 27l and24,l respectively.

The magnet of the brake apparatus shown y isclosed in my Patent,"#744,773, granted November 24, 1903 forvan improvement inelectro-magnets. This apparatus comprises a lurality of armature coressuch as 3,6 an 38 which are arranged in vertical -alinen'ient with coacting fixed cores 35 and 3 7 but at a certain distance therefrom, saiddistance formm an airgap. The fixed cores such as 35 an 37 are providedwith magnet windings 13, 14

. maximum current when the switch 20 is first lamount of current, andthe coil 9, `being in which wlien'energized by an electric curi rent.tend to reduce the air gap and thus raise the movable cores 36 and 38.ll`hese movable cores are connected to almember 40 which is secured to abrake shoe 413. A coil spring 42 bears against the brake shoe 43 and alixed bracket 44 and tends to maintain the movable cores 36, 88 in theirlowermost position with the shoe 43 in engagement with a brake pulley45. 1 do not, however, wish to be limited to the construction of theelectromagnet herein disclosed, as any other suitable alternatingcurrent electromagnet may be used if desired, so long as it accomplishesthe ,object of my invention. Furthermore, an electromagnet operated bypolyphase currents, as, for example, threephase current, may be useditdesired, and in such event the winding may belvaried accordingly.

Referring again Vto F ig. l, it should be noted that the windin 8 isconnected between the lead 5 and tie lead l0 by means or' the conductorsl and 47, whereas the winding 9 is connected between the points 2li and7, so that the current received by the electromagnet B will be dependentupon the current flowing through the brake magnet, coils. As soon as themain line switch Q0 is closed, the lifting coil S of theshort-circuiting magnet A is excited with current frnm a source ofconstant potential between the lead 5 at the point 6 and the lead l0 atthe point 34. The lifting' power of the electroma net is thereforesubstantiallyfconstent rom the time that the main line switch 20 isclosed tothe time that the switch S is automatically closed and themotorhas attained full speed.

The holding coil 9 being connected in series with the brake magnet, willreceive closed, and thus preventthe lifting coil 8 from moving upwardlythe bridge ieee D. As long as the armature of the bra e magnet is in itslower position where the magnetic reluctance is high, due to the airgaps, the brake magnet will take the maximum series with said brakemagnet, will also receive maximum current. In other words, so long asthe brake magnet armature is down and the brake is still applied, themagnetic reluctance is high andthe current through the brake magnet andthrough the holding magnet is consequently at its maximum. The currentthrough the liftingl coil S remains substantially constant and the meansfor operating the switch S is so designed that at this time the holdingelectro# magnet B will overpower the lifting electromagnet A'and preventthe latter from being effective in moving the bridge piece D intoengagement 'with the lixed contacts l a, c and a. lVhen,however,,thebrak` I magnet has lifted its armature and released thebrake, the air gaps of the brake magnet are substantially eliminated,thus materially reducing the magnetic reluctance and increasing theself-induction to such an extent that tlie current through the brakecoils, and consequently through the holding coil 9, will be decreaseduntil the power of the electromagnet B is overcome by the lifting magnetA. Vhen this occurs the bridge piece D will be moved upwardly toelectrically connect the fixed contacts a, a and a, thusshort-circuiting or 'cutting out that portion of the starting resistancewhich is herein shown connected between the points h, g and le.

It should be noted particularly that so long as the lifting coil 8receives current,

the pull of the same on its core l is substant-ially constant, providedthe line voltage remains substantially constant. In case the linecurrent is weak, so that the voltage drops upon the current being drawnfrom 'the line, the lifting magnet will, upon starting, have less pull,but at the same time the holding current will be less also in substan-'phase electromagnets, and the lifting electromagnet may be connectedacross "any two of the mains in a multiphase system; but it ispreferably so yconnected as to effect a good alunne. v

An important feature of my invention and of the arrangement of thecircuits and connections illustrated, is that at first starting there isa high resistance in the secondary or rotor circuit, which naturallydecreases the current taken by the motor to such an extent that the sumof the current in the brake magnet in the down position and the minimumstarting currents of the motor, will notI exceed the sum of the currentsin its up position and the maximum starting current of the motor. Inother words, upon starting the motor by the closing of the main lineswitch 20, the stator will take minimum current by reason of the highresistance in the rotor circuit. At this time, however, the brake magnetand the holding magin the ,brakemagnet windings so that the in an actualdevice which could be constructdependent upon same will take much lesscurrent from the mains. After the brake has been released, only al smallamount of-current necessary to hold the brake apparatus in releasingpo-y sition. The arrangementfmay be such that the brake magnet currentat the start, added to the current taken by the motor at the same time',will be about equal to the sum of the current taken` by the brake magnetand the current taken by the motor after the latter has attained fullspeed. Although I have herein shown only a single embodiment of my;invention, I wish it to be understood that I doA not desire to belimited to any particular construction or arrangement of parts edby.those skilled in the art from the disclosure herein made.

Having fully tlescribed my invention, what I claim and desire to haveprotected by Letters Patent of the United States, is

1. The combination with an alternating current motor, of electromagnetic4brake apparatus for said motor, and means dependent upon the magneticreluctance of said brake apparatus for controlling the. speed of saidmotor.

2. The combination with an alternating current motor, ofelectro-magnetic brake apparatus therefor, and means dependent upon thereluctance of the circuit forsaid brake apparatus for controlling thespeed of said motor, said means being independent of slight variationsof voltage in the main line.

3. The combination with an electric motor, of brake apparatus thereforcomprising a brake magnet, and a differential device the'operation ofsaid brake magnet for controlling the speed of said motor.

4. The combination With an alternating current motor of the inductiontype, of,

brake apparatus comprising an alternating current magnet having amovable armature, and means dependent upon the magnetic reluctance ofsaid magnet for controlling the speed of said motor.

5. The combination with an alternating current motor of the inductiontype, of brake apparatus therefor comprising an electromagnet,electromagnetic means for controlling the speed of said motor, saidelectromagnetic means being electrically connected t0 the brake magnetand controlled by the impedance of the electrical circuit of the latterand operating independently of slight variations of the primary voltage.

6. The combination with an alternating current motor of the inductiontype, of brake apparatus therefor, and means controlled by the magneticreluctance of the brake apparatus for controlling the speed of saidmotor.

opposing electromagnets, and a brake mag- 7. The combination with analternating current motor, of supply mains therefor, starting resistancefor said motor, means for varying the said starting resistance, a brakemagnet, and connections for said brake magnet to effect the operation ofsaid resistance-varying means by the variation in the impedance ofthebrake circuit after the brake has been operated.

8. The combination with an alternating current motor, of anelectromagnet for operating a brake, and means comprising opposingelectromagnets dependent upon the operation of said "brake magnet forcontrollinU the speed of said motor.

9. Tlie combination with an alternating current motor, of a brake magnettherefor,l and a speed-controlling device comprising opposingelectromagnets, oneof said electromagnets being connected to depend forits operation upon said brake-magnet.

- 10. The combination with an alternating current induction motor, of abrake magnet therefor, and an electromagnetic controlling devicecomprising opposing electromagnets operated independent-ly ot' thesecondary circuit.

1l. The combination with an alternating current induction motor, of aspeed-controlling device -for said motor comprising net connected toeffect the variation 'in the strength of one of said electromagnets.

12. The combination With an alternating current motor, of main linesconnected thereto from a source ofv alternating current, ofy anelectromagnetic starting device for the motor comprising opposingelectromagnets, a brake electromagnet, and connections for effecting theenergization of one of said opposing electromagnets by the main linevoltage, and foi-'varying the current through the other opposingelectromagnet of said starting device in accordance with the vvariations of current in said brake electro un magnet.

13. The combination with a multipnase motor of the induction type, ofsupply' mains therefor, an electro-receptive device connected across twoof said mains, a vari- 115 able resistance in the secondary of saidmotor, a brake magnet of the alternating current type, anadditionalelectro-receptive device connected between said brakemagnetand one of the supply mains, and means 1201,.

electroniagnet connected across two of the mains for operating saidswitch, a brake magnet connected across the mains, and a holdingelectroinugnet connected between said brake and one of the mains, saidholding electromagnet acting in opposition to the liftingr electromagnetto preventthe latter from operating the switch until after the brakemagnet has operated and the current in itself and in the holdingelectromagnct has been reduced.

l5. The combination with a three-phase induction motor, of sectionalstarting resistance therefor, a switch for short-circuiting or cuttingout said starting resistance, a lifting electroinagnet connected acrossany two of the mains of said motor and tending to close said switch, atwo-phase or polyphase brake electromagnet connected across the mains,and a holding elcctromalglfnetJ connected between one of the mains andsaid .brake electroinagnet to be dependent upon

